Take a look at Lync Online Web Scheduler for Office 365

Microsoft Lync Online Web Scheduler is a web-based meeting scheduling
and management tool for users who don’t have access to Microsoft
Outlook, or are on an operating system not based on Windows. With Lync
Online Web Scheduler, you can create new meetings, modify your existing
meetings, and send invitations using your favorite email program.

Microsoft Lync Online Web Scheduler is only available for Office 365 users with appropriate subscriptions active.